Abstract
Bone cancer pain (BCP) is the most common type of pain in cancer patients, during which microglia cells were activated. A previous study showed BAM8-22 had the ability to alleviate BCP via inhibiting microglia activation while the mechanism was not clear. This study aims to investigate the specific mechanism of BAM8-22 inhibiting microglia activation. This study was mainly investigated in BCP mice or LPS-treated microglia BV-2 cells. The behavior tests of mice were performed at 0, 1, 2, 12, and 24 h after BAM8-22 treatment. The expression of miR-184 and CX3CR1 mRNAs was detected by quantitative RT-PCR. The expression of CX3CR1 protein and microglia activation marker, Iba-1, was measured by western blot analysis. The levels of TNF-α and IL-1β were detected by ELISA. Dual-luciferase assay was performed to verify the combination between miR-184 and CX3CR1. After BAM8-22 treatment, increased miR-184 level was observed in both BCP mice and LPS-treated BV-2 cells, with the downregulated expression of Iba-1 and inflammatory cytokines, namely the inhibition of microglia activation. The inhibition of miR-184 reversed the inhibitory effect of BAM8-22 on microglia activation. Further, in vitro studies showed that miR-184 bound to the 3′UTR of CX3CR1 and inhibited microglia activation via repressing CX3CR1 expression. What’s more, the suppression of CX3CR1 expression eliminated the reversal effect of the miR-184 inhibitor on BAM8-22-induced microglia activation and decreased Iba-1 expression and pro-inflammatory cytokine secretion. In BCP models, miR-184 was upregulated by BAM8-22 and the elevated level of miR-184 bound to the 3′UTR region of CX3CR1 and repressed CX3CR1 expression, thus inhibiting the microglia activation, suggesting the potential application of miR-184/CX3CR1 for BCP treatment.
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This work was supported by the Natural Science Foundation of Inner Mongolia Autonomous Region (No. 2018MS08066).
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Supplemental Figure 1
Number of spontaneous finches (NSF) and paw withdraw mechanical threshold (PWMT) were examined at five-time points in BCP mice (0, 1, 2, 12, 24 h after intrathecal injection of BAM8-22).*P<0.05 vs 0 h. (PNG 220 kb)
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Wang, A., Tie, M., Guo, D. et al. A Novel Mechanism of BAM8-22 Inhibiting Microglia Activation: Represses CX3CR1 Expression via Upregulating miR-184. J Mol Neurosci 70, 550–558 (2020). https://doi.org/10.1007/s12031-019-01455-0
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DOI: https://doi.org/10.1007/s12031-019-01455-0